Instantaneous starter device for a discharge lamp employing a diode thyristor

ABSTRACT

A starter device for a discharge lamp instantaneously lighting a fluorescent discharge tube; connecting in parallel with said fluorescent discharge tube a starter circuit consisting of a pulse transformer, a capacitor, and a symmetrical diode thyristor or a reverse blocking diode thyristor having a breakover voltage VBO lower than the rated power source voltage but higher than the tube voltage of said fluorescent discharge tube.

United States Patent Inventors Shigeo Koyama Neyagawa-shi;

Masao Yasuda, Higashiosaka-shi; Toru Takei, Osaka; Yasutaka Kawai,Higashiosaka-shi; Takeshi Matsushima, Nara-shi, all 01 Japan Aug. 21,1969 Dec. 7, 1971 Matsushita Electric Industrial Co., Ltd. Kadoma-shi,Osaka, Japan Aug. 27, 1968 Japan Nov. 4, 1968, Japan, No. 43/97146 Appl.No. Filed Patented Assignee Priorities INSTANTANEOUS STARTER DEVICE FORA DISCHARGE LAMP EMPLOYING A DIODE TIIYRISTOR 4 Claims, 11 Drawing Figs.

U.S.Cl 315/101,

315/105, 315/205, 315/207, 315/239, 15/289, 3 IS/DIG. 5

W2- A r r /5 EL r [51] Int. Cl ..II05b 41/18 [50] Field ofSearch 315/100U, 100 H, DIG. 2, DIG. 5, 101, 105, 205, 207, 239, 289

[56] References Cited UNITED STATES PATENTS 3,476,976 11/1969 Morita eta1. 315/101 FOREIGN PATENTS 466,135 6/1950 Canada 315/100 H PrimaryExaminer-Roy Lake Assistant Examiner-Siegfried H. GrimmAttorney-Stevens, Davis, Miller & Mosher ABSTRACT: A starter device fora discharge lamp instantaneously lighting a fluorescent discharge tube;connecting in parallel with said fluorescent discharge tube a startercircuit consisting of a pulse transformer, a capacitor, and asymmetrical diode thyristor or a reverse blocking diode thyristor havinga breakover voltage V lower than the rated power source voltage buthigher than the tube voltage of said fluorescent discharge tube.

PATENTED DEC 71971 SHEET 2 [IF 5 OFF CHARACTE/FVST/C x RES; mmavil wmPATENIEUDEB Han 3.626243 SHEET 5 OF 5 VOL 7/165 CURRENT INSTANTANEGIJSSTARTER DEVICE FOR A DISCHARGE LAMP EMPLOYING A DIODE TIIYIIISTOII Thepresent invention relates to a starter device for a discharge lampinstantaneously lighting a fluorescent discharge tube; connecting inparallel with said fluorescent discharge tube a starter circuitconsisting of a pulse transformer, a capacitor, and a symmetrical diodethyristor or a reverse blocking diode thyristor. Detailed explanation ofthe invention will be made hereinafter with reference to theaccompanying drawings, in which;

FIGS. I and 2 are the electric circuit diagrams of prior art starterdevices for a discharge tube.

FIG. 3 shows the electric circuit diagram of a starter device for adischarge tube according .to one embodiment of the present invention.

FIG. 4 shows the voltage-current characteristic of a symmetrical diodethyristor used in the present invention.

FIG. shows the voltage waveforms across the terminals A and B of thedevice shown in FIG. 3 during starting.

FIG. 6 shows the waveforms of the current flowing through thesymmetrical diode thyristor or at the point A of the device shown inFIG. 3 during starting.

FIG. 7 shows the voltage-current characteristic of a reverse blockingdiode thyristor used in circuit of FIG. 3 and 8 or I1.

FIG. 8 shows the electric circuit diagram of a starter device for adischarge tube according to another embodiment of the present invention.

FIG. 9 shows the voltage waveforms across the terminals A and B of thedevice shown in FIG. 8 during starting.

FIG. III shows the waveforms of the symmetrical diode thyristor orcurrent flowing through the reverse blocking diode thyristor or at thepoint B of the device shown in FIG. 8 during starting.

FIG. Ill shows the practical electric circuit diagram of the circuitshown in FIG. 8.

A conventional starter device as shown in FIGS. 1 and 2 consists of amanual switch 2 or a glow switch 3 connected in parallel with kyvwl[pescent 4ischarge lamp The anual switch is inconvenient because itrequires much time before starting while a glow switch has the problemof a short lifetime although the starting time is faster. In thesefigures, 4 is an AC source, 5 is a power source switch, 6 is a currentlimiting ballast and 7 is a noise preventing capacitor connected inparallel with the manual switch 2 or the glow switch 3. Generally, inorder to instantaneously start a fluorescent discharging tube it isnecessary to provide a sufficient preheating current to both cathodesand at the same time a high continuous or a pulse voltage enough tolight the tube between the opposite cathodes. In the prior art this isattained by winding a cathode preheating winding or a high-voltageapplying winding. However, these methods lead to an increase in the sizeand weight of the current limiting ballast. The efiiciency is reduceddue to an increase in the internal loss. Further, the high cost lowersthe commercial advantage.

Therefore, this invention is aimed-at removing the abovementioneddefects of theprior art and provides a novel starter device for adischarge tube. An embodiment of this invention will be explained withreference to FIGS. 3 to 7 hereinafter. In FIG. 3, 8 is an AC powersource, 9 is a noise preventing capacitor, It is a power source switch,II is a current limiting ballast, I2 is a fluorescent discharge tube,both terminals of which have cathodes l3 and M, I5is a pulse transformerfor generating a pulse voltage consisting of a primary winding 16 and asecondary winding I7, 18 is a symmetrical diode thyristor, and I9 is acapacitor for generating a pulse voltage. The symmetrical diodethyristor I8 has a switching characteristic as shown in FIG. 4. Namely,at a certain voltage (breakover voltage V the symmetrical diodethyristor rapidly changes from the cutoff state to the conducting state.In this circuit, the noise preventing capacitor 9 is connected inparallel with the power source 8 through the power source switch I0, oneend of the power source 8 being connected to one end of the cathode 13of the discharge tube I2 through the current limiting ballast Ill whilethe other end of the power source 8 is connected to the one end ofanother cathode 14 of the discharge tube I2 through the powersourceswitch I0. The other end of the cathode I3 is connected to one end ofthe secondary winding I7 of the pulse transformer 15. The other end ofthe secondary winding I7 is connected to one end of the primary winding16 and also to one end of the capacitor 19. The number of turns of thesecondary winding 17 is larger than that of the primary winding I6 i.e.at a ratio of about 10:1. The other end of the primary winding I6 of thepulse transformer I5 is connected to one end of the symmetrical diodethyristor I8. The other end of a capacitorI9 is connected to the otherend of the symmetrical diode thyristor 18 and connected to the other endof the cathode I4 of the discharge tube 12. Here, it is necessary thatthe primary and secondary windings I6 and 17 of the pulse transformer 15be wound in the same direction.

The breakover voltage V of the symmetrical diode thyristor used in thepresent invention has the characteristic; the rated output voltage ofthe power source 8 the breakover voltage V the tube voltage ofthe'discharge tube 12.

Next, the circuit operation will be explained in detail. In the circuitof FIG. 3, when the power source switch I0 is closed and the conductingstate is reached, a voltage higher than the breakover voltage V i.e. therated output voltage of the power source 8 is applied across bothterminals of the sym metrical diode thyristor 18. Thus, the symmetricaldiode thyristor l8 breaks over to make the circuit conductive. Asufflciently large preheating current flows through the cathodes I3 andI4 of the fluorescent discharge tube 12. In this case the breakover ofthe symmetrical diode thyristor I8 is determined by the breakovervoltage V while the cutoff thereof is determined by a current flowingtherethrough. Due to the inductance of the current limiting ballast IIthe current lags behind the voltage so that the symmetrical diodethyristor becomes conductive over substantially the whole period of thecycle and the power source 8. The voltage waveforms between the points Aand B of the cathodes I3 and 14 become as shown in FIG. 5 while thewaveforms of the current flowing through the thyristor 18 duringpreheating becomes as shown in FIG. 6. A high pulse voltage (about 600V) as shown in FIG. 5 is applied between both terminals of the dischargetube 12 and the preheating of the cathode strikes the discharge of thefluorescent tube 12. Once the discharge tube 12 is lit, the voltageappearing across the symmetrical diode thyristor 18 becomes equal to thetube voltage of the discharge tube 12 so that the symmetrical diodethyristor I8 becomes cutoff. Thus, the discharge tube 12 is maintainedin the discharge state. However, during the lighting of the dischargetube 12 the waveform of the tube voltage has high peak values by theinfluence of the charge and discharge of the capacitor 19. This isenhanced particularly atlow temperatures, and occasionally the peakvalue of the tube voltage exceedsthe breakover voltage V of thesymmetrical diode thyristor 18. Thus, even though the discharge tube I2is lighted and the symmetrical diode thyristor I8 is cutoff, thethyristor recovers its conducting state. As a result, the discharge tube12 returns to the preheating state and does not commence lighting. Inthe practical circuit for the purpose of preventing this inconvenience aresistor (not shown) is connected in parallel with the symmetrical diodethyristor I8 or the capacitor I9. By the insertion of this resistor thedischarge voltage of the capacitor at each cycle is absorbed and hencethe waveform of the tube voltage during lighting is improved. Noreignition phenomenon of the symmetrical diode thyristor 18 takes placeat low tempera tures. Although in the above embodiment has been made ofa symmetrical diode thyristorhaving the characteristic that the cutoffstate rapidly changes to the conducting state at a certain voltage (i.e.breakover voltage V a reverse blocking diode thyristor having a highblocking; power at a negative voltage as shown in FIG. 7 can be used.The breakover voltage V of the reverse blocking diode thyristor usedhere satisfies the condition; the rated output voltage of the powersource breakover voltage V the tube voltage of the discharge tube,whereas the blocking voltage V is sufficiently larger than the ratedpower source voltage. When this reverse blocking diode thyristor isused, a pulsating current flows only in one direction of the circuit.Since a DC component is superposed on this pulsating current, themagnetic circuit of the current limiting ballast saturates so that thefluorescent discharge tube is preheated enough to be lit. The half waveof the power source blocked by the thyristor is applied across thecathodes of the discharge tube. As a result, the same effect can beobtained as in the case of a symmetrical diode thyristor. Furthermore,in the above embodiment a noise preventing capacitor 9 is insertedbetween the input side of the current limiting ballast 11 and the outputside of the cathode 14 of the fluorescent discharge tube 12, i.e.between the points C and D as shown in FIG. 3 in order to obtain thenoise preventing effect. The same effect can be obtained when thecapacitor is inserted between the points A and B. The thyristor 18 andcapacitor 19 may be replaced by each other.

Next, a modified circuit based on the circuit system of FIG. 3 will beexplained with reference to FIGS. 8 to 10. In FIGS. 8, 20 is a powersource, 21 is a noise preventing capacitor, 22 is a power source switch,23 is a current limiting ballast, 24 is a fluorescent discharge tubehaving cathode 25 and 26 on both sides thereof, 27 is a pulsetransformer for generating a pulse voltage consisting of a primarywinding 28 and a secondary winding 29, 30 is a symmetrical diodethyristor, 31 is a capacitor for generating a pulse voltage, and 32 is adiode. The symmetrical diode thyristor 30 has a switching characteristicas shown in FIG. 4. Namely at a certain voltage (breakover voltageV,,,,), the symmetrical diode thyristor rapidly changes from the cutoffstate to the conducting state. In this circuit construction the noisepreventing capacitor 21 is connected in parallel with the power source20through the power source switch 22. One end of the power source 20 isconnected to one end of the cathode 25 of the discharge tube 24 throughthe current limiting ballast 23 while the other end of the power source20 is connected to one end of the other cathode 26 of the discharge tube24 through the power source switch 22. The other end of the cathode 25is connected to one end of the secondary winding 29 of the pulsetransformer 27. The other end of the secondary winding 29 is connectedto the end of the primary winding 28 and together to one end of thecapacitor 31. The number of turns of the secondary winding 29 of thepulse transformer 27 is larger than that of the primary winding 28 inthe ratio of about :1. One end of the symmetrical diode thyristor 30 isconnected to the other end of the primary winding 28 of the pulsetransformer 27. The other end of the capacitor 31 is connected to theother end of the symmetrical diode thyristor 30 and the positiveelectrode side of the diode 32. The negative electrode side of the diode32 is connected to the other end of the other cathode 26 of thedischarge tube 24. Here the diode 32 may be connected in the reversedirection.

The breakover voltage V of the symmetrical diode thyristor 30 used inthis invention has the characteristic; the rated output voltage of thepower source 20 breakover voltage V the tube voltage of the dischargetube 24. The reverse breakover voltage of the diode 32 is sufficientlylarger than the rated output voltage of the power source 20.

Next the circuit operation will be explained in detail. In the electriccircuit shown in FIG. 8, when the power source switch 22 is closed andthe conducting state is reached, a higher voltage than the breakovervoltage V i.e. the rated output voltage of the power source 20, isapplied between both terminals of the symmetrical diode thyristor 30.Thus, the symmetrical diode thyristor 30 breaks over to make the circuitconductive. A preheating current from the cathodes half wave rectifiedby the diode 32 flows through the cathodes 25 and 26 of the fluorescentdischarge tube 24. The voltage waveform applied between the points E andF of the cathodes 25 and 26 of the fluorescent discharge tube 24 duringpreheating becomes as shown in FIG. 9 while the waveform of the currentflowing through the thyristor 30 during preheating becomes as shown inFIG. 10. A high pulse voltage as shown in FIG. 9 appears between bothterminals of the discharge tube 24 i.e. between the cathodes 25 and 26.So, due to the preheating effect of the cathodes 25 and 26 the dischargetube 24 is effectively lit. Once the discharge tube 24 is lit, thevoltage appearing across the symmetrical diode thyristor 30 becomescutoff. Therefore, the discharge tube 24 maintains the discharge state.Here even if the peak value of the tube voltage waveform of thedischarge tube 24 is extremely high or has a large temperaturedependence, the capacitor 31 is charged only in the DC direction by thediode 32. Therefore, the bad influence on the peak value of thedischarge tube 24 due to the charge and discharge of the capacitor 31and on the symmetrical diode thyristor 30 can be prevented.

Although in the above embodiment explanation has been made of the casewhere one end of the secondary winding 29 of the pulse transformer 27(i.e. the beginning of the winding) is connected to one end of thecathode 25 of the discharge tube 24 and the other end (i.e. the end ofthe winding) is connected to one end of the primary winding (i.e. theend of the winding), there is no trouble when the secondary winding isconnected in the opposite direction. However, it is necessary that thesecondary winding 29 and the primary winding 28 are connected in thesame direction. Further, it is allowed that the symmetrical diodethyristor 30 and the capacitor 31 are reversely connected.

Although in the embodiment shown in FIG. 8 explanation has been made ofa case where the starting element is a symmetrical diode thyristor, areverse blocking diode thyristor having the characteristic as shown inFIG. 7 may be employed. The breakover voltage of the reverse blockingdiode thyristor satisfied the condition; the rated output voltage of thepower source breakover voltage V the tube voltage of the discharge tube,whereas the blocking voltage V is sufficiently larger than the ratedpower source voltage. The current flowing through the circuit in thecase of the reverse blocking diode thyristor is a pulsation current inone direction superposed on a DC current. Therefore, the magneticcircuit of the current limiting ballast becomes saturated and thefluorescent discharge tube is preheated enough to be lit. The half waveof the power source blocked by the thyristor is applied across thecathodes of the discharge tube. As the result, the same effect can beobtained as in the case with the symmetrical diode thyristor. It isneedless to say here that the reverse blocking diode thyristor isconnected in the same direction as the diode. Furthermore, in the aboveembodiment the noise preventing capacitor 21 inserted between the inputside of the current limiting ballast 23 and the output side of thecathode of the discharge tube 24, i.e. between the points G and H hasthe effect of preventing the noise.

FIG. 11 shows a circuit diagram where winding 23' for increasing thecathode preheating current is employed together with the currentlimiting ballast 23 of FIG. 8.

In the starter device of the present invention constituted as mentionedabove, the addition of such auxiliary means fitted to the startingdevice to further improve the starting characteristic, i.e. the windingwound around the current limiting ballast for increasing the cathodepreheating current shown in FIG. 11 and the existence of the adjacentconductor near the discharge tube, does not needless to say depart fromthe spirit of this invention.

Thus, the inventive use of the symmetrical diode thyristor or reverseblocking diode thyristor as the starter element for lighting thedischarge tube has a semipermanent life due to the semiconductor and amuch more miniaturized size compared to the conventional glow starterdevice. Therefore, the weight can be reduced. Since no large currentlimiting ballast is used, the internal loss is diminished. In addition,more rapid starting is effected.

What is claimed is:

l. A starter device for a fluorescent discharge lamp having first andsecond cathodes, each of said cathodes having first and second ends,comprising a. a current limiting ballast connected in series with anelectric power source between the first ends of said first and secondcathodes,

b. a pulse transformer having primary and secondary and second ends,comprising a. a current limiting ballast connected in series with anelectric power source between the first ends of said first and secondcathodes,

windings wound in the same direction, each of said 5 b. a pulsetransformer having primary and secondary windings having first andsecond ends, windings wound in the same direction, each of said c. firstconductive means coupling a first end of the seconding a ing st andSecond ends,

dary winding of said transformer to the second end of said 6- s ndu ians coupling a first end of the Sec nfirst cathode, the second end ofaid e o dar indi dary winding of said transformer to the second end ofsaid being onne ted to the nd d f id primary i d. first cathode, thesecond end of said secondary winding ing, being connected to the secondend of said primary windd. a reverse blocking diode thyristor, g, e. acapacitor coupled in series with said thyristor across the a Symmetricaldiode thyrlstofr primary winding of said transformer, and e. a capacitorcoupled in series with said thyristor across the f. second conductivemeans coupling the junction of said P 'f Y g a tran f0rrner, and ithyristor and capacitor to the second end of said second dlode onlycouplmg the J of said and h d capacitor to the second end of said secondcathode. 2 A starter device as d fi d by claim 1 wherein Said 4. Asecond device as defined by claim 3 wherein said first Second conductivemeans comprise a diode conductive means comprises an auxiliary windinginductively 3. A starter device for a fluorescent discharge lamp havinga Coupled to Sam current hmmng first and second cathodes, each of saidcathodes having first

1. A starter device for a fluorescent discharge lamp having first andsecond cathodes, each of said cathodes having first and second ends,comprising a. a current limiting ballast connected in series with anelectric power source between the first ends of said first and secondcathodes, b. a pulse transformer having primary and secondary windingswound in the same direction, each of said windings having first andsecond ends, c. first conductive means coupling a first end of thesecondary winding of said transformer to the second end of said firstcathode, the second end of said secondary winding being connected to thesecond end of said primary winding, d. a reverse blocking diodethyristor, e. a capacitor coupled in series with said thyristor acrossthe primary winding of said transformer, and f. second conductive meanscoupling the junction of said thyristor and capacitor to the second endof said second cathode.
 2. A starter device as defined by claim 1wherein said second conductive means comprise a diode.
 3. A starterdevice for a fluorescent discharge lamp having a first and secondcathodes, each of said cathodes having first and second ends, comprisinga. a current limiting ballast connected in series with an electric powersource between the first ends of said first and second cathodes, b. apulse transformer having primary and secondary windings wound in thesame direction, each of said windings having first and second ends, c.first conductive means coupling a first end of the secondary winding ofsaid transformer to the second end of said first cathode, the second endof said secondary winding being connected to the second end of saidprimary winding, d. a symmetrical diode thyristor, e. a capacitorcoupled in series with said thyristor across the primary winding of saidtransformer, and f. a diode only coupling the junction of said thyristorand capacitor to the second end of said second cathode.
 4. A seconddevice as defined by claim 3 wherein said first conductive meanscomprises an auxiliary winding inductively coupled to said currentlimiting ballast.